It affects the feel. Being in 2/4 would imply that the bar had 2 main beats rather than 4 (it would have a 2 feel rather than a 4 feel). Writing in 2/4 would be equivalent to writing in 2/2 at double the tempo, not 4/4 at double the tempo.

So, the decision over whether to use 2/2 or 2/4 is a matter of preference, and there's no difference as far as feel is concerned. If, for example, writing it in 2/4 meant having lots of teeny 32nd notes, it might be better to double the note values and use 2/2, as this might be easier to read.

yep. It's all a preference of feel and how the drummer plays (and how everyone else plays for that matter...). For instance, you could have a song in 7/4 time, but it might also work as a measure of 3/4 and a measure of 4/4.. or 4/4 and 3/4.

Like the end of Frank Zappa's "Echidna's Arf (of you)". It would work if it was still in 4/4 time... but switching to 5/16 makes way more sense based on what everyone is playing.

Great topic!
This actually came up at a big band rehearsal not long ago.We were reading a chart of "God Rest Ye Merry Gentlemen" in 11/4 time, with measures of 6 and 10 thrown in(for good measure) The drummer & I agreed it was confusing written in 4 and shudda been in 8.
There's a definite difference in the quality of a quarter beat or eighth beat-irrespective of tempo or number of written notes. I can feel it, but I cant describe the theory. I suspect it deals with accents, strong-weak beats, and deep in my subconscience something says triplets.
any word from those in the know?